The present invention is directed to a defect inspection system and, more particularly, high speed defect detection utilizing near and mid-infrared imaging, high speed image processing, comparison and contrast, processed image evaluation and characterization, and the development of control signals for sorting or separating objects or items based on the defect determination. More particularly, the present invention relates to methods of near and mid-infrared imaging for fruit defect inspection and fruit stem-end and calyx identification.
U.S. Pat. Nos. 5,339,963 and 5,533,628 each issued to Yang Tao and assigned to Agri-Tech, Inc., are each hereby incorporated by reference, and describe methods and apparatus for sorting objects by color, and in particular are directed to the sorting of apples. The color sorting apparatus has a singulator section, a color sorter, and a conveyor which drops the sorted objects into appropriate collection bins. The objects for sorting are transported on an endless conveyor through the singulation and color sorting section. An independently adjustable speed belt rotates in the same direction as the wheels and operates to provide a view of each of the four sides of the object to an imaging device such as a camera which supplies red, green and blue signals to an image processor which performs a color transformation and obtains a single composite hue value for each object or piece of fruit to be sorted. Based on a comparison of the hue value to the user program grading criteria, signals are provided to the conveyor so that the objects are ultimately deposited in the appropriate sorting bins.
U.S. Pat. No. 5,732,147, issued to Yang Tao and assigned to Agri-Tech, Inc., is hereby incorporated by reference and describes an image processing system using cameras and image processing techniques to identify undesirable objects on roller conveyor lines. The cameras above the conveyor capture images of the passing objects (such as apples). The roller background information is removed and images of the objects remain. To analyze each individual object accurately, the adjacent objects are isolated and small noisy residue fragments are removed. A spherical optical transformation and a defect preservation transformation preserve any defect levels on objects even below the roller background and compensate for the non-lambertian gradient reflectants on spherical objects at their curvatures and dimensions. Defect segments are then extracted from the resulting transformed images. The size, level and pattern of the defect segments indicate the degree of defects in the object. The extracted features are fed into a recognition process in a decision-making system for grade rejection decisions. The locations and coordinates of the defects generated by defect allocation function are combined with defect rejection decisions and user parameters to signal appropriate mechanical actions such as to separate objects with defects from those that do not contain defects.
Conventional attempts at using laser scanning and reflectance to detect line shifts or changes in height of the object in order to attempt to detect defects in fruit or other objects have not been successful and are not accurate due to the inability to provide the same orientation of each object, changes in size and shape between individual pieces or items of fruit, and the like.
Still further, it has been difficult to differentiate between true defects such as bruises, limb rub, bulls-eyes, fungus such as black net, blemishes, cuts, injuries, stem punches, cracks, worm holes, insect damage, disease damage, color defects, Russet and the like from the fruit stem-end, stem, calyx, or blossom. Hence, there is a need for an improved method and apparatus for defect detection, fruit, such as apple, defect detection as compared to detection of the stem-end, stem, and/or calyx identification, defects in smooth surfaces, and/or defect detection and object or item sorting or separation based thereon.
In accordance with the present invention, a method and apparatus is provided which addresses the drawbacks of the prior art and which incorporates two separate imaging devices, one near-infrared and one mid-infrared imaging device which simultaneously capture images of the passing objects or items. The background information is removed and images of the objects remain. A spherical optical transform and a defect preservation transform preserve any defect levels on objects and compensate for the non-lambertian gradient reflectants on spherical objects at their curvatures and dimensions.
The mid-infrared or middle infrared camera is used at about 3-5 microns or 8-12 microns to provide an image of the stem-end, stems, and/or calyx but is insensitive to true defects. Near-infrared at about 700-1000 nanometers (nn) is used to provide an image of stem-end, stems, calyx, and defects.
In accordance with the present invention, the processed images provided by the mid-infrared camera are subtracted from the images provided by the near-infrared camera to produce an image of just defects which are analyzed to produce the item or object separation or sorting control signals based on defect rejection decisions and user parameters to signal appropriate mechanical actions (driver commands) to separate objects with defects from those that do not contain defects, or to sort or categorize objects based on the amount, type, size, or character of the defects.
In accordance with the present invention, a complete defect detection system for sorting, separating, or grading apples can be constructed for about $100,000.00 or less. In as much as the present invention is based on the use of infrared imaging devices, such as cameras, the temperature of at least a portion of the exterior surface of each item or object to be inspected must be raised by about 5-15xc2x0 C. or more so that the cameras can provide an image of a difference in temperature between outer smooth surface and the cavity at the stem-end, the stem, and calyx of an apple or a similar depression, cavity, protrusion, or the like in another object or item. In accordance with one embodiment of the present invention, heated brush rollers are used to quickly heat the exterior of apples passing along a conveyor to provide the necessary change in temperature to allow the cameras to provide an image of defects, stem-end, stem, and/or calyx.
Although the present invention is especially adapted for use in inspecting and detecting defects in items or objects, such as apples and other fruits and vegetables such as pears, tomatoes, peaches, apricots, and other stone or pit foods having stem ends, stems, blossom ends, calyx, or the like, the present invention also finds applicability in inspecting and detecting defects in other items or objects, such as manufactured parts such as cups, dishes, balls, golf balls, bearings, molded plastic items, and the like having smooth surfaces, pits, posts, or the like.
The present invention provides a system which is effective, fast, has high resolution, and which has a greater accuracy and discrimination rate than prior art devices or systems.
The principal object of the present invention is the provision of a method and apparatus for the detection and discrimination of defects in items or objects such as apples.
Another object of the present invention is the provision of a method and apparatus for sorting items or objects based on the character, number, type or aggregation of defects.
A still further object of the present invention is the provision of a method and apparatus for discriminating between stem-end, stems, and calyx as compared to true defects.
Other objects and further scope of the applicability of the present invention will become apparent from the detailed description to follow, taken in conjunction with accompanying drawings wherein like parts are designated by like reference numerals.